The present invention relates generally to the field of hydraulic circuits within an automatic transmission of a land vehicle and, more particularly, to a Torque Converter Clutch (hereinafter “TCC”) Apply Valve for GENERAL MOTORS 4T65-E and other similar transmissions that directs torque converter fluid pressure to the TCC apply and release circuits to actuate the torque converter clutch.
Automatic transmission systems of the prior art have a hydraulic circuit sub-system which includes at least a hydraulic pump, a valve body having fluid conducting passageways or circuits, input and exhaust ports formed within the fluid circuits, and a plurality of “spool” valves so-called because of their resemblance to sewing thread spools. Such spool valves are comprised of modified, cylindrical pistons which alternately open and close fluid ports within the valve body to regulate the flow and pressure of automatic transmission fluid (hereinafter “ATF”) within the fluid circuits to actuate various components of the transmission. It will be understood that in describing hydraulic fluid circuits, ATF usually changes names when it passes through an orifice or control valve in a specific circuit.
ATF leakage within the TCC apply and release circuits occurs due to the constant oscillation and abrasive action of the TCC apply valve within the mating bore of the aluminum valve body, which results in a loss of converter apply pressure. The loss of pressure in the apply circuit causes TCC slippage, converter shudder, and eventually an overheated and/or burned torque converter. Thus, the present invention has been developed to resolve these problems and other shortcomings of the prior art.
There are known prior art patents and a pending patent application that are available in the field of hydraulic control valves. One example of a torque converter clutch (TCC) apply valve is disclosed in pending U.S. patent application Ser. No. 10/187,092 to Stafford (currently on appeal) which discloses a TCC apply valve including an apply piston having an expandable seal installed thereon at the primary wear location within the valve body to reduce ATF leakage. This valve piston also includes an internal ATF gallery with radially extending passages formed therein in fluid communication with an annular groove wherein the expandable seal resides. Whenever the present TCC Apply Valve is actuated by the TCC solenoid, TCC signal pressure forces ATF into the gallery in the apply valve piston and further urges the seal radially outward into contact with the bore to minimize ATF leakage during the apply cycle of the torque converter clutch.
Another example of a hydraulic valve having a structural feature in common with the present invention is disclosed in U.S. Pat. No. 6,736,747 to Stafford which teaches a forward clutch control valve assembly for a Ford AX4N transaxle including a primary control land having an increased outside diameter and axial length, which replaces the narrow forward stem of the original equipment valve piston. The increased axial length of the primary control land on this valve piston is based on the limits of axial travel of the piston within the cylindrical bore wherein the valve piston resides during operation. This forward clutch control valve assembly also provides a substantially increased control land-to-bore surface contact ratio and an increased end face surface area. As a result this present forward clutch control valve assembly is substantially less prone to bending and/or seizure within its mating bore during operation.
While these devices fulfill their respective, particular objectives and requirements, the aforementioned patents do not disclose the Torque Converter Clutch Apply Valve of the present invention, which substantially departs from the conventional concepts and designs of the prior art.